Lovers come and go. Friends remain for ever. That's the myth, anyway

We expect marriages to get rocky and families to provoke pain. But friends tend to be presented in a mostly happy light: think Sex and the City, or Friends. Bumps and scrapes between Samantha and Charlotte are in the plot but only so they might be resolved. Lovers come and go. Friends remain.

This idealisation does not help us in real life, where friendships do not just have entertaining ups and downs, but disturbing fights and bitter endings. Such a reality is demonstrated in new research based on data collected from the Mass Observation Project, just published in The Sociological Review.

Prof Carol Smart and her colleagues argue that some friends can be dumped quite easily. These are "simple friendships" – people we know for fun, say, so when the fun ceases the relationship is dropped or drifts away. But "complex friendships" – people to whom we were close, as soulmates – prove more distressing.

One woman is typical when she confessed that she stuck with an old friend out of responsibility:

"I have an ongoing friendship with a divorced man … who is a good friend in many ways, but who can be very overbearing, loud and insensitive … and he has an anxiety problem. I am sorry for him but find myself totally drained after a day in his company."

The idealisation of friendship comes through in the research too. Some insisted that you should not abandon old friends, ever. "I'm loyal towards my friend," said one participant, before admitting: "This sounds awful, but I don't get a lot out of the friendship any more." Another person made the arresting observation that the way someone talks about their friends opens a window into the soul, "through which a person's moral calibre could be assessed".

Interestingly, the research advises caution when it comes to reconnecting with old friends. Meeting college or childhood friends can "call up the ghost of former selves, causing regret, embarrassment and discomfort".

Part of the problem is that friendship has no institutionalised life course. When you fall in love, you will think about moving in, about engagement, about marriage, about children, about divorce, about how to get along with your ex. The pathway is not trekked by everyone, of course. But the marital pattern provides a template against which to chart your love life, even when you honour it in the breach. Further, the institutional nature of marriage and marriage-like relationships means that help can be sought when things go wrong.

Not so with friendship because the course of a friendship has no such pattern or support. That is part of its appeal, in fact – friendship as the relationship of freedom. You did not choose your family. You realise that you had little conscious sense of why you chose your lover, once the romance quietens. But you did choose your friends, apparently. And then something goes wrong. You are left floundering.

Perhaps there should be friendship counselling too. It would recognise that friendship is vital to human wellbeing because this form of human love gets under our skin quite as much as any other, for good and ill. But in the meantime, the philosopher Friedrich Nietzsche has a useful metaphor to offer.

He knew a thing or two about amity's calamities, having once been a friend of Wagner. The experience of the break-up seems to have led Nietzsche to develop the notion of "star friendship".

Stars are distant, like the friendships of yesteryear. They look bright, as you remember the good times. But the great thing about stars is that they don't cast a shadow over you now. So too might old friendship, once a blessing, now broken. It is not easy to find the place where they don't cast a shadow of guilt or bitterness or loss. But the star metaphor might keep you headed in a better direction. It holds out the hope that one day you will wake up and realise that you're over the friendship, it was good, and all will be well.